As protesters throughout the Arab world challenge their authoritarian leaders, Iraqis, government officials and regional experts see increasing signs that Prime Minister Nuri Kamal al-Maliki is expanding his power, undermining the fragile democracy struggling to take hold here.

A ruling in January by Iraq’s highest court — sought by Mr. Maliki — gave him control of once-independent agencies responsible for running the country’s central bank, conducting elections and investigating corruption.A month after that ruling, two leading human rights groups reported that forces that report directly to Mr. Maliki, in violation of the country’s Constitution, were running secret jails where detainees had been tortured.

And in July, Iraq’s high court ruled that members of Parliament no longer had the power to propose legislation. Instead, all new laws would have to be proposed by Mr. Maliki’s cabinet or the president and then passed to the Parliament for a vote.Political experts said they knew of no other parliamentary democracy that had such restrictions.

With influence from the United States waning as the military prepares to withdraw at the end of the year, Mr. Maliki’s critics say that one legacy of the eight-year American occupation is a democratically elected leader from the country’s Shiite majority who has far more power than the Constitution intended.

Critics said that the court ruling in January was a particularly damaging blow to the country’s voting process and feeble economy. Sean Kane, the program officer for Iraq at the United States Institute of Peace, a Congressionally financed research center, said that the decision appeared to contradict Iraq’s Constitution, which he said states that the commissions have varying levels of responsibility to Parliament.

Referring to the recent court ruling, Aliya Nasaif, a lawmaker from the Iraqiya coalition, a rival to Mr. Maliki’s State of Law bloc, said: “Because there is no law, you will find him overwhelming other institutions. This is the beginning of dictatorship. We are regressing by centuries.”Mr. Maliki has tried to respond to public discontent by giving his Cabinet 100 days to come up with ways to improve services. He has also promised to cut his pay and not seek a third term in 2014.

An official for the United States Embassy said that Mr. Maliki and his advisers were trying to signal that they understood the outrage of Iraqis over corruption and poverty.Those concessions, however, have done little to mollify Iraqis, and thousands took to the streets last week, sometimes violently, to protest the government’s failure to provide electricity and jobs.

Rights groups criticized the government for what they called a violent crackdown on those demonstrations, saying that scores of people — including journalists — were beaten and detained.On Friday, protesters took the streets again, although there were far fewer reports of violence. Nevertheless, in the southern city of Basra, several journalists at a protest reported they had been beaten by security forces.

Mr. Maliki, an uncharismatic but canny politician who was elected prime minister in 2006, has been credited with helping reduce the violence that once threatened to tear Iraq apart.But his critics say those victories have come at a cost. They accuse Mr. Maliki of taking a stronger hand over Iraq’s powerful police and military by leaving the slots of defense and interior minister open indefinitely, allowing him to act as the head of both agencies.

“The developments in recent months have provoked real concern across the Iraqi political spectrum, and the responsibility now rests largely with the Parliament to check the prime minister’s power,” said Jason Gluck, a rule of law adviser at the United States Institute of Peace and an adviser to the Iraqi Parliament in 2007. “Whether the diverse political parties in Parliament can effectively do so will be a critical test for Iraq’s burgeoning democracy.”

One of Mr. Maliki’s top advisers, Ali al-Moussawi, said that the once-independent agencies had “irregularities and problems” in the past because of “the lack of supervision.”Mr. Moussawi said the new oversight would focus on administrative matters but would not interfere with the overall missions of the institutions.“The noise against the court decision is for political reasons,” Mr. Moussawi said. “Those who make this noise are not doing it for the sake of these bodies but for political gains.”

Mr. Maliki had been seen as a fairly weak leader until 2008, when he ordered an Iraqi military offensive against Shiite militias, which had taken control of parts of southern Iraq. His critics say he continued to strengthen his power by using his security forces to resolve political disputes, particularly in Kurdistan.

Mr. Maliki narrowly lost in the March 2010 election and appeared significantly weakened. But he muscled his way to a second term after favorable decisions from the election commission and the high court, allowing him to assemble a wide-ranging coalition government in December.

Joost Hiltermann, an Iraq expert for the International Crisis Group, said that Mr. Maliki had benefited from the fact that Iraq has not been a top priority for the Obama administration.Some members of Iraq’s fractious Parliament, a rubber-stamp institution under Saddam Hussein, have said they would take measures to check Mr. Maliki’s power, vowing to cut funds to security agencies controlled by the prime minister and to pass laws that limit him.

None of those attempts, however, have gained much traction, in large part because the opposition is so divided.The degree of the court’s independence is unclear. The Iraqi Constitution is vague on how members of the court can be removed and appointed, and what guarantees its independence.

Officials with the election commission said they were baffled by the court’s decision that placed them under Mr. Maliki’s supervision. They also worried that Iraqis would lose faith in the credibility of local and national elections if Mr. Maliki’s office began to select election monitors or to change the rules governing where voting takes place, how ballots are counted and who runs polling stations.

Faraj al-Haidari, head of Iraq’s election commission, said that United Nations officials had expressed their concern about the ruling to him.Shortly after the decision was handed down, Mr. Haidari said he had received a letter from Mr. Maliki’s office telling the commission to halt the appointments of 38 low-level election officials. He said the commission had refused.

Fear has also extended to the central bank, where officials said they worried that Mr. Maliki would now have the power to order the institution to print money to cover Iraq’s growing budget deficits. Such a move would weaken the value of Iraq’s anemic currency and lead to rapid inflation.

“Our fear is that they will now see it as their money,” said the bank’s senior adviser, Mudher M. Salih Kasim.